I was reading about the types of diodes, including those that can be used to generate microwaves, and I found myself confused about the material I found on it. This link discusses the differences between three kinds of diodes, but I'm simply having trouble interpreting these diagrams that I come across, because I'm unclear about what p+ and n+ mean vs p and n in a diagram. I think that p and n are used to represent positively and negatively doped semiconductor material, but I'm unclear with these diagrams that use pluses and minuses in addition to n and p.

  • 2
    \$\begingroup\$ p+ and n+ just means "extra" or "heavily doped." A minus would mean lightly doped. \$\endgroup\$ – jonk Jan 16 '18 at 4:45

Most semiconductor device processes have a few doping levels available for the designer to use. Instead of working with the actual concentrations, it's easier to work with p+ vs. p to say it has more acceptors. N+ will similarly have more donors.

It's very common in semiconductor physics to go even further and use: n--, n-, n, n+, n++ or p--, p-, p, p+, p++ to talk about doped regions.

Eg. We could be working with an extremely P lowly doped substrate (p--) in which you have a pwell (p-) and the contact to the pwell is made with a highly doped diffusion region (p+).

  • \$\begingroup\$ I see. Would you still need to have some specific dopant ratio for the device to produce a certain frequency? Does the size of the device determine the operating voltage? \$\endgroup\$ – Tom Jan 16 '18 at 14:47
  • \$\begingroup\$ If you want to calculate anything you'll still need the doping concentrations. The notation is usually used in diagrams to explain the basic operation. \$\endgroup\$ – Sven B Jan 18 '18 at 14:47

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.